[PATCH, MIPS] Fix *_SUB instruction macros

[Joseph S. Myers]

On Wed, 7 May 2014, Steve Ellcey  wrote:

> While doing some work in glibc, I noticed that some of the *_SUB instruction
> macros in sysdeps/mips/sys/asm.h are defined to do addition instructions
> instead of subtraction instructions.  I don't know why this is but it seems
> obviously wrong and it is different then the definitions in the linux kernel
> which do define these as subtract instructions (arch/mips/include/asm/asm.h).
> 
> This patch changes the macros to do sub instructions instead of add.
> 
> OK to checkin?

OK, but please file a bug in Bugzilla first (and the use the [BZ #N] 
notation in your ChangeLog entry, add the bug to the list of fixed bugs in 
NEWS and close the bug after checking in the fix), since this was a 
user-visible bug in releases.

-- 
Joseph S. Myers
joseph@codesourcery.com